Effects of Achillea Plant Essential Oil and Some Rhizobium Bacteria Inoculation on Soil Enzyme Activity in Bean (Phaseolus vulgaris) Plant.

Essential oils are generally used to prevent plant diseases and fungal diseases. However, little is known about the effects on soil enzyme activity.

The objective of this study is to determine the effects of different doses of essential oils (EO₀: 0.0 ppm, EO₁₀₀: 100 ppm, EO₁₀₀₀: 1000 ppm) isolated from Achillea millefolium plants and different Rhizobium bacteria inoculations (Rhizobium leguminosarum biovar phaseoli F7, R. leguminosarum biovar phaseoli F83, R. leguminosarum biovar phaseoli Ciat 899) on soil enzyme activity (urease, acid phosphatase and alkaline phosphatase, dehydrogenase, β-glucosidase) in planted sugar bean (Phaseolus vulgaris) soils.

Soils were collected from the research farm of Ataturk University 0-20 cm depth and potted. Seeds were planted and essential oils in different doses were slowly added over the top soil in each pot with water. During the 60 days incubation period, soil moisture content was kept at field capacity. The pots were watered to 60% water-holding capacity and were maintained at this moisture content by watering to weight every 2–3 days.

According to the research, soil enzyme activities were shoved significant (p<0.01) differences as statistically in different Rhizobium bacteria applications and essential oil concentrations.

The highest urease enzyme activity was observed at Ciat 899 bacteria application and EO₀ ppm essential oil concentration (44.89±2.7 µg NH₄-N g^-1 soil 2h^-1). The lowest urease enzyme activity was observed at F7 bacteria application and EO₁₀₀₀ ppm essential oil concentration (30.80±0.9 µg NH₄⁺ g soil 2h^-1).

The highest acid and alkaline phosphatase enzyme activities were observed at Ciat 899 bacteria applications and EO₀ ppm essential oil concentrations (17.34±1.3 and 30.42±1.9 µg PNP g^-1 soil h^-1, respectively). The lowest acid and alkaline phosphatase enzyme activities were observed at F7 bacteria applications and EO₁₀₀₀ ppm essential oil concentrations (11.12±0.7 and 20.33±1.2 µg PNP g^-1 soil h^-1, respectively).

The highest dehydrogenase enzyme activity was observed at F7 bacteria application and EO₀ ppm essential oil concentration (20.20±1.0 µg TPF g^-1 soil 24 h^-1). The lowest dehydrogenase enzyme activity was observed at Ciat 899 bacteria application and EO₁₀₀₀ ppm essential oil concentration (13.01±0.8 µg TPF g^-1 soil 24 h^-1).

The highest β-glucosidase enzyme activity was observed at Ciat 899 bacteria application and EO₀ ppm essential oil concentration (309.26±7.8 µg PNP g^-1 soil h^-1). The lowest β-glucosidase enzyme activity was observed at F7 bacteria application and EO₁₀₀₀ ppm essential oil concentration (117.520±4.7 µg PNP g^-1 soil h^-1).

All soil enzyme activities generally increased with Rhizobium bacteria inoculation, but, decreased with increasing essential oil concentration in all applications as control.

Key words: Achillea, Essential Oil, Rhizobium inoculation, soil enzyme activity